Is ONE PIECE episode 452 filler?
Canon No, episode 452 of ONE PIECE is canon.
#452
To the Navy Headquarters! Off to Rescue Ace!
目指せ海軍本部 エース救出への船出！
Aired 23 May 2010
Mochibayo compiled this list from MyAnimeList's labels, because MyAnimeList's episode data is not reaching us at the moment.